The subject invention relates generally to optical fiber spectrometry and more specifically to the fluorometric detection of polyhalogenated hydrocarbons.
The detection and measurement of bound halogens and halogen related compounds in human and animal tissues and in industrial effluents is of vital importance for health and environmental purposes. Many common household and industrial chemicals in every day use, such as dry cleaning agents, refrigerants like freon, fire extinguishers, paint removers, fumigants, polymeric compounds, anesthetics such as halothane, enfluorane, metoxofluorane and isofluorane, and some antihelmintics, certain pesticides and fungicides contain toxic, halogenated organic compounds which are either ingested or discharged into the environment, making these chemicals a potential, and in most instances, a real health and environmental hazard. It has thus become important to be able to detect and even quantitatively measure or monitor the presence of these compounds or their metabolic products, so that the levels of their ingestion or discharge into the environment may be controlled.
As a consequence, several methods and instruments have been devised to measure these halogen containing organic compounds. Some of these methods for detecting gaseous halohydrocarbons use electron capture or piezo electric devices. Some other methods have been devised to detect organic halocomponds, especially in the liquid or aqueous phase. One such method is based on the reaction of halogenated hydrocarbons with pyridine or pyridine derivatives in an alkaline medium to yield highly colored products. It is known in the art that when a gem-polyhalogen compound, which is a compound that carries more than two halogen atom on the same carbon, is heated with pyridine in a strongly alkaline medium (pH 10-11), such as in the presence of sodium or potassium hydroxide, an intensely red product, exhibiting absorption maxima at about 368 mu and at about 535 mu, is formed. This reaction scheme, shown in equation 1 below, ##STR1## is known as the Fujiwara reaction (K. Fujiwara, Sitzfer, Abhandl. Naturforsch. Ges. Rostock., 6, 33, (1941); G. A. Lugg, Anal. Chem., 38, 1532 (1966); T. Uno et al., Chem. Pharm. Bull., 30, 1876 (1982)). The Fujiwara reaction has become a classic method for the detection of halogenated hydrocarbons in a given sample or analyte in the liquid phase. However, for a quantitative measure of halogenated hydrocarbons in an analytical or test solution or sample, the Fujiwara reaction presents some problems, due to the insolubility of pyridine in reagents normally used to generate the necessary alkalinity and the difficulty in being able to control the rate of diffusion of the OH.sup.- ion from the aqueous phase into the organic pyridine phase.
More often, the reaction consists of a two-phase procedure whereby the gem-polyhalogen compound, pyridine and aqueous sodium or potassium hydroxide are combined, mixed, and heated for a predetermined length of time until an intensely red color develops. The pyridine phase is then separated from the alkaline phase by conventional methods. Absorption spectra of the colored product are measured thereafter. The amount of the chromophoric product formed is dependent on the amount and rate of diffusion of the hydroxide ion into the pyridine phase of the mixture. Since this diffusion is difficult to control, reproducibility of measurements becomes extremely difficult and unpredictable.
A one phase procedure using pyridine-water-sodium hydroxide has also been employed to avoid the pitfalls of the two phase method (G. A. Lugg, supra). There have also been several modifications of the Fujiwara reaction, such as different solvents, different bases, varying temperatures, varying concentrations of sodium hydroxide, time of reaction and the like, to minimize the difficulties encountered and to make the reaction more widely accessible.
U.S. Pat. No. 3,472,626 issued to Law, discloses a method for the detection of organic halogen containing compounds in aqueous liquids, by the use of the salt of a pyridine base and either caustic soda or caustic potash.
Still other problems are encountered in the measurement of these halogenated hydrocarbons or their metabolic products in environmental and tissue samples. These compounds are found at extremely low levels in tissues, groundwater samples or effluents, which tend to make the reproducibility and reliability of any measurements difficult. It would also be desirable some times to be able to analyze these samples at a discharge site which is remote from the site of the detection equipment and continually monitor the levels of these compounds in various samples from a remote monitoring site.
Laser based remote fiber spectroscopy offers a wide range of possibilities for the in situ detection and quantification of not only halohydrocarbons but also other groundwater contaminants. The development of high transmission, long range fiber optics and the advantages of their use in data transmission have made fiber optical methods of data transmission and detection extremely attractive. The use of such fiber optics also makes it possible to trasmit or receive data signals over distances of two or three kilometers.
It would, therefore, be desirable to have a fiber optic sensor and detection system, for the measurement of organic halohydrocarbons in tissue and environmental samples, which would not only be sensitive to measure low levels of these compounds but which would also be amenable to operation from a remote location.
Accordingly, it is an object of the subject invention to provide a method for the measurement of organic halohydrocarbons in environmental and tissue samples.
Another object is to provide a method whereby the levels of organic halohydrocarbons in tissue, ground water and other environmental samples can be continually monitored.
Yet another object is to provide an apparatus and method which enable the simultaneous monitoring of organic halohydrocarbons in multiple samples of groundwater and other environmental material and tissue samples, from a remote location.
Still another object is to provide a sensor and detection system which can detect not only low levels of organic halohydrocarbons but can also be operated from a remote location.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.